Two-stage process for the conversion of tar sand to liquid fuels and specialty chemicals

ABSTRACT

A process is disclosed for converting Tar Sand to fuels and/or valuable chemicais. The process comprises the steps of a) activating Tar Sand to make it more susceptible to conversion; c) partially converting the Tar Sand to a solubilized material; and d) subjecting the unconverted Tar Sand to a second conversion step. The process optionally comprises a step b) of adding a solvent to the activated Tar Sand. In a preferred embodiment the solubilized Tar Sand obtained in step c) is removed before the unconverted Tar Sand is subjected to step d).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the conversion of hydrogen-poor fluid hydrocarbons to liquid fuels and specialty chemicals.

It has long been recognized that hydrogen-poor fluid hydrocarbons such as tar sands, oil shales, and heavy crudes, in particular tar sands, are abundantly available and form a potential source of liquid fuels and valuable chemicals.

It is known to distill the lighter fractions off these hydrogen-poor fluid hydrocarbons to obtain a material similar to crude oil. This distillate is then further processed as one would a regular crude. This is an inefficient approach, as it leaves a significant portion of the starting material in an unconverted state.

It is far more desirable to find a way for converting virtually all of the hydrogen-poor fluid hydrocarbon to liquid fuel and valuable chemicals.

There is a need for a low-cost process that is able to convert a large proportion of the hydrocarbons present in hydrogen-poor fluid hydrocarbons under conditions that are mild enough to avoid high equipment and energy costs and/or substantial degradation of the conversion products.

Hydrogen-poor fluid hydrocarbons are characterized by a high viscosity, which makes them difficult to process. It is desirable to develop processes that are able to process these hydrocarbons without requiring expensive equipment or demanding processing conditions in terms of temperature and pressure.

SUMMARY OF THE INVENTION

As used herein, the term “Tar Sand” means hydrogen-poor fluid hydrocarbon materials, and encompasses tar sand per se, oil sand, oil shale, heavy crude oil, bottoms from refinery processes, and the like. In general, these materials contain less than 15% hydrogen, often only about 10% hydrogen.

The present invention relates to a process for converting Tar Sand to a liquid fuel comprising the steps of:

-   -   a) activating the Tar Sand to make it more susceptible to         conversion;     -   b) optionally, adding a solvent;     -   c) partially converting the activated Tar Sand to form         solubilized material;     -   d) subjecting unconverted Tar Sand from step c) to a conversion         process.

Due to the activation taking place in step a), optionally aided by the addition of a solvent (step b), step c) can be carried out under mild conditions. As a result the product obtained in step c) is not substantially degraded. Unconverted Tar Sand from step c) is subsequently subjected to a second conversion in step d). Optionally, and preferably, converted Tar Sand obtained in step c) is removed from the unconverted Tar Sand before the latter is subjected to a second conversion in step d). If conversion products from step c) are first removed, step d) may be carried out under more severe conditions than step c). In the alternative, step d) may be preceded by a second activation step so that the unconverted Tar Sand is more susceptible to the conversion process of step d).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an embodiment of the process of the present invention.

FIG. 2 is a schematic diagram of an alternate embodiment of the process of the present invention.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The following is a description of certain embodiments of the invention, given by way of example only.

The present invention relates to a process for converting Tar Sand to a liquid fuel comprising the steps of:

-   -   a) activating the Tar Sand to make it more susceptible to         conversion;     -   b) optionally, adding a solvent;     -   c) partially converting the activated Tar Sand to form         solubilized material;     -   d) subjecting unconverted Tar Sand from step c) to a conversion         process.

The process provides the general advantage of requiring less severe process conditions than, for example, traditional HTU or pyrolysis processes. Accordingly, the process is more cost-effective and requires simpler less expensive equipment. The process is also environmentally more acceptable, and produces product of higher quality, and more suitable for conversion to fuels and chemicals.

Particular embodiments of the process provide homogenous, intimate mixtures of Tar Sand material with a solvent and/or a solid and/or a liquid additive, which provides advantages for subsequent conversion.

One important aspect of the process of the present invention is that it removes easily converted components of the Tar Sand material from the reaction mixture after a first conversion, allowing other, more difficultly converted components to be subjected to somewhat more severe conversion conditions without exposing the products already obtained to undesired degradation.

Overall, the process of the present invention results in better yields of products of a better quality than has heretofore been possible, and does so at a lower consumption of energy and lower capital equipment costs.

Although the process is described herein in the context of the production of liquid fuels, it will be understood that the process may be used for converting Tar Sand to feedstock chemicals, specialty chemicals, nano-composites, construction materials, cardboard and paper products, and the like.

Step a) of the process generally involves providing an intimate mixture of the Tar Sand with a solvent, a particulate solid and/or liquid material, or both a solvent and a particulate solid material. If the material is an oil shale it is desirable to reduce the particle size of the Tar Sand by processes such as milling, grinding, and the like.

Processes for providing intimate mixtures of Tar Sand material are described in Patent Applications EP 061135638 and EP 061135810, the disclosures of which are incorporated herein by reference. An alternate process involves the use of an extruder and/or a kneader. Kneading is very suitable to provide homogeneous and intimate mixing and allows for reactions to take place, while extrusion provides high shear mechanical treatment of the materials. In particular the use of a screw extruder is preferred for use herein, because it allows for operation at high pressures without requiring expensive equipment.

It will be understood that the mixing step may be combined with the process of reducing the particle size of the Tar Sand material. For example, ball milling or grinding of the Tar Sand in the presence of a particulate solid material will result in an intimate mixture of the Tar Sand and the particulate solid material.

Focusing now on the use of an extruder and/or kneader for the purpose of activating the Tar Sand, it is possible to operate the process at increased temperature. Many screw extruders are provided with a heating mantle through which steam or heated oil may be circulated. It is also possible to inject steam into nozzles provided in predetermined locations of the barrel. Steam injection provides a combined effect of heating the Tar Sand and adding a solvent (water).

The pressure inside the extruder is determined by the viscosity of the mass within the extruder, the design of the screw within the extruder (for example, a tapered pitch screw provides a higher pressure than a constant pitch screw), and the design of the perforated plate at the outlet of the extruder. The back pressure provided by this plate is a function of the amount of open area in relation to the amount of closed area, with lower open area/closed area ratios providing greater back pressure.

If a single pass through an extruder does not provide sufficient mixing, two or more extruders may be provided in series, or the material may be subjected to two or more passes through one extruder. Similarly, the capacity of a plant may be readily increased by operating two or more extruders in parallel.

Suitable solvents for use in step b) include water, alcohols (in particular ethanol and glycerol), bio-oil or other products from the subsequent conversion of the Tar Sand, liquid acids, aqueous solutions of acids and bases, liquid CO₂, and the like. Water is the preferred solvent in most applications, because of its availability, low cost, and ease of handling. Liquids that are produced during the subsequent conversion of the Tar Sand are also readily available and may be preferred for that reason.

Suitable solid materials for use in step a) include solid acids and bases, salts, minerals, clays, layered materials, and the like. Solid materials having catalytic properties are preferred. Examples include metal oxides, metal hydroxides, alkaline and alkaline earth oxides, hydroxides, carbonates, hydroxyl carbonates, hydrotalcite-like materials, etc. As has been noted earlier, it may be desirable to add several solid materials to the Tar Sand, or a combination of one or more solid materials and one or more solvents.

It is possible to add precursors of inorganic solids, and causing them to solidify or even crystallize during the mixing process. For example, certain inorganic solids may precipitate from solution in response to an increase in temperature or a change in pH. An increase in temperature may be effected in the kneader by heating the barrel, or by injecting steam. A pH change may be effected by injecting a solution of an acid or a base. Similarly, amorphous materials may be caused to crystallize by increasing the temperature of the mixture.

As mentioned above, the addition of a solvent is optional. For example, in many cases water is the solvent of choice. Many forms of Tar Sand contain sufficient quantities of water for the present purpose, obviating the need for adding additional solvent. It may even be desirable to remove water during the activation step. This may for example be accomplished by heating the Tar Sand to a temperature above 100° C., and letting off steam via pressure valves located along the barrel of the extrude, if an extruder is used in the process.

In many cases conversion step c) commences while the activated Tar Sand is still being processed in the kneader or extruder or in both. If this process is not completed in the kneader, the activated Tar Sand may be processed further in a second kneader, or it may be subjected to a second pass through the first kneader. Alternatively, the Tar Sand may be transferred to a different processor to complete step c). A suitable example of such a processor is a filter press, which can be operated at desirable conditions of temperature and pressure.

It is highly preferred that liquid products resulting from conversion step c) be separated from unconverted Tar Sand. The purpose of this separation is two-fold. Firstly, it reduces the mass of material that needs to be subjected to further conversion in step d), which makes the operation of step d) more efficient. Secondly, it avoids subjecting liquid conversion products from step c) to the subsequent conversion process, avoiding a degradation of this liquid product by such further processing.

In a specific embodiment, part of the first conversion takes place in a filter press under conditions of increased temperature and pressure. This may be accomplished by loading the activated Tar Sand into a filter press, and injecting steam to increase both the temperature and the pressure. After this first conversion step is completed the filter press is de-pressurized over a filter medium, such as a filter cloth or screen, and the reaction product is separated into a liquid filtrate stream and a filter cake. The liquid stream comprises solvent and liquid conversion product, as well as fine particles of unconverted Tar Sand. The filter cake comprises unconverted Tar Sand, retained solvent, and liquid reaction product.

As used herein, the term “unconverted Tar Sand” refers to Tar Sand that has not been converted to a liquid product in step c). The term includes Tar Sand material that has not undergone any chemical conversion. The term also includes Tar Sand that has undergone some conversion, but insufficient to form a liquid. For example, hydrocarbons may have been converted to hydrocarbons of a lower average molecular weight, but still be semi-solid. This would be considered “unconverted Tar Sand” within the meaning of this term as used herein. Such a material may well be an “activated unconverted Tar Sand” if its molecular weight is reduced and/or its macro and/or micro structure has changed, in a way that makes it more susceptible for conversion to a liquid product in step d).

In the alternative the liquid may be separated from remaining solids by nano-filtration or membrane separation. Instead of a filtration technique an extractive separation may be used.

The unconverted Tar Sand is subjected to a second conversion process in step d). If the liquid conversion product of step c) is removed from the unconverted Tar Sand prior to step d), this second conversion may be carried out under more severe conditions than the first conversion, without risking degradation of reaction products already formed. For example, the unconverted Tar Sand may be subjected to a conventional HTU or pyrolysis process.

In a preferred embodiment of the process of the present invention, the unconverted Tar Sand is activated prior to step d) so that step d) may be carried out under less severe conditions than the prior art HTU and pyrolysis processes. In many cases the unconverted Tar Sand from step c) is already activated, for example because inorganic particulate materials added in step a) are carried over with the unconverted Tar Sand into step d). The unconverted Tar Sand may also be activated as a result of a partial conversion in step c), insufficient to render the Tar Sand liquid, but sufficient to make it more susceptible to further conversion.

Any conversion process is suitable for use in step d). HTU and pyrolysis have already been mentioned; desirably, these processes are conducted under conditions as mild as the activation of the Tar Sand will permit. Gasification may be a desirable option, for example to create gaseous fuel for meeting the heat requirements of the overall process.

In most cases, both steps c) and d) produce a mixture of liquid hydrocarbons, which may be converted to suitable liquid transportation fuels in modified refinery processes such as fluid catalytic cracking, hydroconversion, thermal conversion, and the like. In these processes the Tar Sand derived liquid hydrocarbons may be the sole feedstock, or they may be blended with conventional, crude oil-based feedstocks.

In another embodiment the activation step a) is conducted in a kneader/extruder assembly in the presence of an inorganic solid, for example an alkaline or alkaline earth metal oxide or hydroxide, and the product of step c) is hydrothermally treated in step d). The inorganic material which is homogenously mixed in step a)/step b) is thus most effectively dispersed and present in steps c) and/or d) in intimate contact with the unconverted Tar Sand, resulting in an efficient conversion. Said solids may possess catalytic properties that further enhance the conversion process.

In another embodiment the inorganic additive introduced in step a) may be simply a heat transferring medium, like for example sand, clay or a mineral, ore or soil, which may have also catalytic properties. In this case the product of step c) can be subjected to a pyrolysis conversion process. The advantage of this process is that here the heat transfer medium is in close and intimate contact with the Tar Sand in a dispersed form.

In another embodiment the activation in step a) may involve the addition of an acid or a base, which, aided by the application of heat and/or steam, will break down the compact structure of the Tar Sand composite, rendering it more susceptible to a subsequent conversion, for example by acid hydrolysis and/or enzymatic conversion.

In another embodiment the Tar Sand in step a) containing water and optionally an additive is heated above 100° C., while being mechanically treated, so that the water is allowed to evaporate.

In another embodiment, the Tar Sand is mechanically processed in the presence of other carbonaceous materials such as coal, lignite, and biomass in step a) and step b) optionally with the addition of additives, followed by gasification of the unconverted materials.

In another embodiment the Tar Sand is intimately mixed with an additive in a ball mill, grinding the components together to form the activated Tar Sand. Optionally a liquid solvent can be added.

In another embodiment the Tar Sand is grinded with an additive in a fluidized and/or spouted bed, as disclosed in U.S.60/831,220, the disclosures of which are incorporated herein by reference. Optionally a liquid solvent can be added.

In another embodiment the unconverted Tar Sand of step c) is converted to paraffins suitable for diesel fuels.

In another embodiment the unconverted Tar Sand of step c), which often appears to be the fibrous crystalline cellulose coated with an additive, is converted to materials suitable for paper, board or construction materials

In another embodiment the unconverted material (mainly crystalline cellulose) is converted to a transportation fuel by aqueous phase reforming as suggested by Huber et al., see: G. W. Huber, J. N. Chheda, C. J. Barrett, J. A. Dumesic, Science 308 (2005) 1446.

In another embodiment the solubilized material is converted to a transportation fuel by aqueous phase reforming as suggested by Huber et al., see: G. W. Huber, J. N. Chheda, C. J. Barrett, J. A. Dumesic, Science 308 (2005) 1446.

In another embodiment the unconverted material of step b and/or c) is first submitted to electromagnetic and/or ultrasound energy, optionally in the presence of a polar solvent such as ethanol. Following this treatment the so activated material is converted by any of the above means.

In another embodiment the unconverted material of step b and/or c), which comprises a material susceptible to the absorption of electro-magnetic radiation is first submitted to electromagnetic optionally in the presence of a polar solvent such as ethanol. Following this treatment the so activated material is converted by any of the above means.

In another embodiment the unconverted material of step b and/or c) is first submitted to intimate mixing with an additive, optionally in the presence of a solvent such as ethanol. Following this treatment the so activated material is converted by any of the above means.

FIG. 1 shows one particular embodiment 100 of the process of the present invention. Tar Sand 101 and catalyst 102 are mixed in mechanical mixer 110, with the optional addition of solvent 103. After mixing the mixture is transferred to a first reactor 120, for a first, partial, conversion step. This conversion step is carried out under mild conditions.

The partially converted mixture 121 is transferred to a first product recovery means 130. Optionally solvent 105 is added at this stage. Reaction product 106 is separated from the mixture, and removed for further processing. The removal of reaction product 106 ensures that reaction product 106 is not subjected to the subsequent, more severe conversion in reactor 140.

The unconverted portion 131 of the mixture is transferred to a second conversion reactor 140, where it is subjected to a more severe conversion reaction. Optionally, additional catalyst 107 is added at this stage. Optionally also, solvent 108 may be added.

Finally, reaction product 109 is recovered from reactor 140.

FIG. 2 shows an alternate embodiment 200 of the process of the present invention.

Tar Sand 201 and catalyst 202 are mixed in mechanical mixer 210, with the optional addition of solvent 203. After mixing the mixture is transferred to a first reactor 220, for a first, partial, conversion step. This conversion step is carried out under mild conditions.

The partially converted mixture 221 is transferred to a first product recovery means 230. Optionally solvent 205 is added at this stage. Reaction product 206 is separated from the mixture, and removed for further processing. The removal of reaction product 206 ensures that reaction product 206 is not subjected to the subsequent, more severe conversion in reactor 240.

The unconverted portion 231 of the mixture is transferred to a second conversion reactor 240, where it is subjected to a more severe conversion reaction. Optionally, additional catalyst 207 is added at this stage. Optionally also, solvent 208 may be added.

Reaction product 209 is recovered from reactor 240, and combined with reaction product 206 for further processing in refinery process 250. Process 250 may comprise any number of conventional refinery processes, such as fluid catalytic cracking (FCC), hyrotreatment processing (HTP), thermal cracking (TC), and the like.

Thus, the invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art. 

1. A process for converting Tar Sand to fuels and/or chemicals comprising the steps of: a) Activating the Tar Sand to make it more susceptible to conversion; b) Optionally adding a solvent; c) Partially converting the activated Tar Sand to form solubilized material; d) Subjecting the unconverted Tar Sand from step c) to a conversion process.
 2. The process of claim 1 wherein step a) comprises the addition of an inorganic material.
 3. The process of claim 1 wherein step a) comprises the addition of an organic material.
 4. The process of claim 2 wherein the inorganic material is in particulate form.
 5. The process of claim 2, wherein the inorganic material is selected from the group consisting of cationic clays, anionic days, natural clays, hydrotalcite-like materials, layered materials, ores, minerals, metal oxides, hydroxides of metals of the alkaline and alkaline earth groups, and mixtures thereof.
 6. The process of claim 1 wherein step a) comprises adding one or more additives that react to form a new phase.
 7. The process of claim 6 wherein at least one of the additives added in step a) reacts to form a new crystalline phase.
 8. (canceled)
 9. The process of claim 6, wherein the Tar Sand in step a) is in particulate form, and at least one of the additives added in step a) reacts to form a new phase distributed within the Tar Sand particle.
 10. The process of claim 1 comprising, after step c) and before step d), the additional step of separating unconverted Tar Sand from the solubilized material.
 11. The process of claim 10 wherein the separation involves a filtration device, such as a filter press, a centrifuge, a membrane filter, or a nano-filter. 12-14. (canceled)
 15. The process of claim 2 wherein the inorganic material has catalytic properties.
 16. The process of claim 3 wherein the organic material has catalytic properties. 17-25. (canceled)
 26. The process of claim 1 wherein the conversion process of step d) is a hydrothermal process.
 27. The process of claim 1 wherein the conversion process of step d) is a pyrolysis process or a flash pyrolysis process.
 28. The process of claim 1 wherein the conversion process of step d) is a gasification process.
 29. The process of claim 1 wherein the conversion process of step d) is a refinery process selected from the group consisting of gasification, thermal cracking, catalytic cracking, hydrocracking, and combinations thereof.
 30. The process of claim 1 wherein the conversion process of step d) involves more than one process step.
 31. The process of claim 1 wherein the conversion of step d) is a gasification process producing a synthesis gas, and wherein the synthesis gas is subsequently converted into a liquid hydrocarbon mixture.
 32. The process of claim 1 comprising the additional step of converting the product of strep d) and/or step c) to a liquid fuel, suitable for use in an internal combustion engine.
 33. The process of claim 32 wherein the additional step comprises conversion in a unit selected from an FCC unit, a Hydrocracking unit, a Hydrotreating unit, a Thermal Cracking unit, and combinations thereof
 34. The process of claim 1 wherein is the product produced in step c) and/or step d) is blended with crude-oil derived hydrocarbons prior to processing in a refinery.
 35. The process of claim 1 wherein step d) comprises converting the unconverted Tar Sand to electrical energy.
 36. The process of claim 1 wherein, prior to step d), the unconverted Tar Sand from step c) is submitted to electromagnetic and/or ultrasound energy, optionally in the presence of a polar solvent.
 37. The process of claim 1 wherein, prior to step d), the unconverted Tar Sand from step c) is submitted to intimate mixing with an additive, optionally in the presence of a solvent. 